Saw Palmetto for Enlarged Prostate?

Feb. 8, 2006 -- Extracts of the saw palmetto berry may not ease symptoms of an enlarged prostate, a new study shows.

Saw palmetto extracts are widely used for symptoms of enlarged prostate. However, the U.S. government doesn't hold herbal products to the same standards as prescription medicines.

The study, published in The New England Journal of Medicine, compared a saw palmetto extract to a placebo pill, which contained no medicine or saw palmetto. The saw palmetto pills showed no advantage over the placebo in the yearlong study.

"In this study, saw palmetto did not improve symptoms or objective measures of benign prostatic hyperplasia," write the researchers. They included Stephen Bent, MD, of the Osher Center for Integrative Medicine at the University of California, San Francisco.

About 2.5 million U.S. adults report taking saw palmetto, according to statistics cited in Bent's study.

About the Study

Participants were 225 men aged 49 and older with moderate to severe symptoms of enlarged prostate. Enlarged prostates are common in older men. About half of all men over 50 experience some symptoms, and almost all men are affected as they age.

The condition isn't due to cancer. Though enlarged prostates are usually harmless, they can interfere with urination.

The researchers randomly assigned the men to take one or the other pill twice daily for a year. No one knew which men were taking the real saw palmetto pills, which came in doses of 160 milligrams.

Saw palmetto has a distinct taste and appearance. Bent's team copied those traits in the placebo pills so no one would guess which pill was which. The saw palmetto pills came from one batch and were chosen by an advisory committee of the National Center for Complementary and Alternative Medicine, part of the National Institutes of Health.

The men rated their symptoms (including urinary flow) and quality of life before and during the study. Other objective measures such as prostate size, residual urine left after voiding, and blood tests were also checked.

Study's Results

The saw palmetto pills were no better than the placebo at easing the men's symptoms, quality of life, or other objective measures, the study shows.

Other studies have shown that saw palmetto helps ease the condition's symptoms, such as improving urinary flow, Bent's team notes. Those studies may not have used placebos that closely resembled the saw palmetto pills, the researchers note.

At the end of Bent's study, the men were asked which pill they thought they'd taken. Most were mistaken. Forty percent of men taking saw palmetto correctly guessed that they'd gotten saw palmetto. In the placebo group, 46% thought they were taking saw palmetto, the study shows.

Their guesses suggest that the placebo pills had passed for the real thing, the researchers note, adding that side effects were similar in both groups.